Method for scaling control in a membrane system operation via a control system of a plant

Abstract

A method is disclosed for scaling control in a membrane system operation. The method can be performed by a model in the control system of a plant. The method can include selecting one or more antiscalants corresponding to one or more components of the scale, based on one or more of feed water condition, membrane material, membrane fouling status and a kinetic study relating to a reaction between the antiscalants and the components of the scale. The composition of one or more selected antiscalants can be estimated based on an overall scaling rate constant.

We claim: 
     
       1. A method for scaling control in a membrane system operation by a control system of a plant, wherein the control system comprises (i) a flow controller for varying a flow rate of one or more antiscalants and (ii) one or more sensors installed in the plant for measuring plant data including at least one of feed flow rate, feed pressure, feed concentration, reject flow rate, reject pressure, product flow rate, and product concentration, the method comprising:
 selecting, by the control system, one or more antiscalants corresponding to one or more types of scale components, based on feed water condition, membrane material, and a kinetic study relating to a reaction between the one or more antiscalants and the one or more types of scale components, wherein selecting the one or more antiscalants comprises determining an overall rate constant based on water quality and antiscalant flow rate; 
 estimating, by the control system, a composition of the one or more selected antiscalants and a dosage of the estimated composition of the one or more selected antiscalants based on the overall rate constant, membrane fouling status, and an objective function, wherein the objective function includes a first term for estimating the composition of the one or more selected antiscalants, a second term for minimizing cost of antiscalant, and a third term for selecting antiscalant flow rate in administering the dosage of the estimated composition of the one or more selected antiscalants, wherein the membrane fouling status is determined based on a model for estimating membrane transport parameters using the plant data measured by the one or more sensors, and wherein estimating the dosage of the estimated composition of the one or more selected antiscalants comprises determining one or more set-points for the flow controller; and 
 administering, by the flow controller, the estimated dosage of the estimated composition of the one or more selected antiscalants for scaling control in the membrane system operation based on the determined one or more set-points for the flow controller; 
 wherein the kinetic study relating to the reaction between the one or more antiscalants and the one or more types of scale components is derived using a shrinking core model including chemical reaction control and solid particle mass transfer diffusion control. 
 
     
     
       2. The method as claimed in  claim 1 , wherein the selecting of one or more antiscalants is based on a membrane manufacturer list of antiscalants. 
     
     
       3. The method as claimed in  claim 1 , wherein estimating the composition of one or more selected antiscalants comprises:
 calculating, by the control system, the overall rate constant using offline plant measurements. 
 
     
     
       4. The method as claimed in  claim 1 , wherein administering the dosage of the estimated composition of one or more selected antiscalants is based on a membrane fouling status. 
     
     
       5. The method as claimed in  claim 1 , wherein the membrane fouling status is determined based on an estimation of at least one time varying physical parameter of the membrane. 
     
     
       6. The method as claimed in  claim 5 , comprising:
 estimating, by the control system, the time varying physical parameters of the membrane based on the plant data. 
 
     
     
       7. The method as claimed in  claim 5 , wherein the time varying physical parameters include at least one of:
 hydrodynamic permeability of the membrane and solute permeability of the membrane. 
 
     
     
       8. The method as claimed in  claim 4 , wherein the membrane fouling status is determined based on an estimation of at least one time varying physical parameter of the membrane. 
     
     
       9. The method as claimed in  claim 3 , wherein the offline plant measurements include at least one of water quality, antiscalant flow rate and antiscalant concentration.